Fostering of Sound Water Cycle -Countermeasures for watershed flood and drought-
Urbanization which is unsound for water cycle
Recently, rainfall-induced floods have frequently occurred in urbanized cities and surrounding areas.
Other problems including water deficiency, groundwater depletion, and river water contamination have also become worse.
These problems are actually caused by disturbance in water cycle systems.
Urban development and urbanization have caused water environment disturbances.
■Natural water cycle：
The ground has great water-retaining and penetration capacities.
Rainwater penetrates into the soil, while this controls the amount of rainwater flowing directly into rivers. Penetrated water slowly flows into rivers as groundwater and spring water.
■Disturbance in water cycle：
The surface runoff amount increases because of urbanization.
The rainwater that penetrates into the soil significantly decreases, while the flow rate into rivers increases. For this reason, increase in precipitation causes a rise in the river level in a short time. This situation causes difficulty in drainage capacities of small and middle rivers, while causing inside water inundation. This also causes insufficient height and strength in rivers, resulting in causing floods.
Urban environment-friendly rainwater storage penetration technique
■Easing of urban flood disasters and nature restoration: Water environment-friendly development
Rainwater penetration under the soil controls surface runoffs and prevents floods from occurring. Furthermore, rainfall penetration enriches groundwater, and maintains high river levels.
■Types and efforts of the rainwater storage penetration technique
The rainwater storage penetration technique brings the water cycle close to the natural cycle system. This technique is effective not only to flood prevention, but also to drought prevention, river water purifying, and urban heat island.
●See the details of the rainwater storage penetration technique→
●See the details of the rainwater storage penetration technique→
Relationships between urbanization and rainfall
In the past, rainwater has naturally penetrated into the ground. However, as urbanization advances, the land surface has been covered with asphalt or concrete. This disturbs the penetration of rainwater into the ground. As a result (of increase in surface runoffs), the rainwater flow rate downstream increases (with growing burden on sewer systems), and rainwater flows into rivers immediately after the beginning of rainfall in a short time. This increases the risk of flooding (increasing the peak flow rate). Urbanization has also caused various problems, such as decline in rainwater in normal times and decrease in groundwater levels.
Conventional rainwater treatment methods and problems
In order to deal with these problems, rainwater storage facilities including control basins have been installed and the existing rivers have been improved. However, recent ground situations and pollution due to construction projects have made it difficult to implement rainwater treatment measures. The rainwater storage penetration technique was studied and developed in order to improve these circumstances.
Major features
1. Control of rainwater runoffs out of the area
The total rainwater runoff amount is decreased.
The peak flow rate is decreased.
The time between the beginning of rainfall and the occurrence of rainwater runoff is delayed. (Burden on rivers eliminated)
2. Increase in groundwater and environmental preservation
The amount of groundwater is restored to the natural state, and the soil is prevented from becoming dry.
The soil ecosystem is preserved.
Normal river waters are maintained.
3. Possibilities including design rationalization
Control basins are reduced, and efficiency of sports grounds used also as rainwater storage is enhanced.
Burdens on downstream river improvement and sewer work are reduced.
Use of penetration products to regular water channels and pipe lines can make work easier and reduce work cost.
4. Thermal environmental improvement
Cooling of the earth's surface due to vaporization heat is promoted, while urban heat island is controlled.
Content
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448-1 Kusabe, Sannancho, Tanba City, Hyogo Pref., Japan 6693151
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448-1 Kusabe, Sannancho, Tanba City, Hyogo Pref., Japan 6693151
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Design, development, production, and sale of concrete products
